The present invention relates to rotary mowers and more specifically relates to blade drive spindles for such mowers.
The spindle assemblies dealt with here include a shaft having a hub integral with or somehow secured to one end thereof. There are a variety of spindle assemblies of this type, however, either their energy absorbing ability is not such as to preclude part breakage, the coming off of parts or undue support bearing loads resulting in early failure, when the blade impacts fixed objects or their cost of manufacture is to much.
One known design, for example, employs a shaft having a threaded end on which a hub is received. An annular thread relief recess is provided in the shaft at the end of the threads receiving the hub. A threaded axial bore is provided in the end of the shaft for receiving a blade mounting bolt which operates against a spring washer for snubbing a blade tightly against the hub. In this design, impact loading of the spindle causes it to break at the recess in the shaft.
Another known design overcomes the drawback of the design just mentioned by eliminating the threads and thread recess at the end of the shaft and instead securing the hub to the shaft by welding. This design is too expensive, however, since it requires various surfaces of the hub and shaft to be remachined to the correct dimensions after the welding operation.
In another known design, the shaft is solid and the hub is keyed to the end of the shaft. This design too is strong enough to withstand impact loading without breakage, but, because it is loaded beyond its bearing support, it is easily bent and the bearings are subject to early failure.